Chapter 6. Internationalization and themes - JBoss Seam 1.1.0 bate1 英文参考手册

Each user login session has an associated instance of java.util.Locale (available to the application as a session-scoped component named locale). Under normal circumstances, you won't need to do any special configuration to set the locale. Seam just delegates to JSF to determine the active locale:

It is possible to set the locale manually via the Seam configuration properties localeSelector.language, localeSelector.country and localeSelector.variant, but we can't think of any good reason to ever do this.

It is, however, useful to allow the user to set the locale manually via the application user interface. Seam provides built-in functionality for overriding the locale determined by the algorithm above. All you have to do is add the following fragment to a form in your JSP or Facelets page:

<h:selectOneMenu value="#{localeSelector.language}">
    <f:selectItem itemLabel="English" itemValue="en"/>
    <f:selectItem itemLabel="Deutsch" itemValue="de"/>
    <f:selectItem itemLabel="Francais" itemValue="fr"/>
</h:selectOneMenu>
<h:commandButton action="#{localeSelector.select}" value="#{messages['ChangeLanguage']}"/>

Or, if you want a list of all supported locales from faces-config.xml, just use:

<h:selectOneMenu value="#{localeSelector.localeString}">
    <f:selectItems value="#{localeSelector.supportedLocales}"/>
</h:selectOneMenu>
<h:commandButton action="#{localeSelector.select}" value="#{messages['ChangeLanguage']}"/>

When this use selects an item from the drop-down, and clicks the button, the Seam and JSF locales will be overridden for the rest of the session.

JSF supports internationalization of user interface labels and descriptive text via the use of <f:loadBundle />. You can use this approach in Seam applications. Alternatively, you can take advantage of the Seam messages component to display templated labels with embedded EL expressions.

Each login session has an associated instance of java.util.ResourceBundle (available to the application as a session-scoped component named resourceBundle). You'll need to make your internationalized labels available via this special resource bundle. By default, the resource bundle used by Seam is named messages and so you'll need to define your labels in files named messages.properties, messages_en.properties, messages_en_AU.properties, etc. These files usually belong in the WEB-INF/classes directory.

So, in messages_en.properties:

Hello=Hello

And in messages_en_AU.properties:

Hello=G'day

You can select a different name for the resource bundle by setting the Seam configuration property named resourceBundle.bundleNames. You can even specify a list of resource bundle names to be searched (depth first) for messages.

<component name="resourceBundle">
    <property name="bundlenames">
        <value>mycompany_messages</value>
        <value>standard_messages</value>
    </property>
</component>

If you define your labels in this special resource bundle, you'll be able to use them without having to type <f:loadBundle ... /> on every page. Instead, you can simply type:

<h:outputText value="#{messages['Hello']}"/>

or:

<h:outputText value="#{messages.Hello}"/>

Even better, the messages themselves may contain EL expressions:

Hello=Hello, #{user.firstName} #{user.lastName}

Hello=G'day, #{user.firstName}

You can even use the messages in your code:

@In(create=true) private Map<String, String> messages;

@In("#{messages['Hello']}") private String helloMessage;

The facesMessages component is a super-convenient way to display success or failure messages to the user. The functionality we just described also works for faces messages:

@Name("hello")
@Stateless
public class HelloBean implements Hello {
    @In(create=true) 
    FacesMessages facesMessages;
    
    public String sayIt() {
        facesMessages.addFromResourceBundle("Hello");
    }
}

This will display Hello, Gavin King or G'day, Gavin, depending upon the user's locale.

There is also a session-scoped instance of java.util.Timezone, named timezone, and a Seam component for changing the timezone named timezoneSelector. By default, the timezone is the default timezone of the server. Unfortunately, the JSF specification says that all dates and times should be assumed to be UTC, and displayed as UTC, unless a timezone is explicitly specified using <f:convertDateTime>. This is an extremely inconvenient default behavior.

Seam overrides this behavior, and defaults all dates and times to the Seam timezone. In addition, Seam provides the <s:convertDateTime> tag which always performs conversions in the Seam timezone.

Seam applications are also very easily skinnable. The theme API is very similar to the localization API, but of course these two concerns are orthogonal, and some applications support both localization and themes.

First, configure the set of supported themes:

<component name="themeSelector">
    <property name="availableThemes">
        <value>default</value>
        <value>accessible</value>
        <value>printable</value>
    </property>
</component>

Note that the first theme listed is the default theme.

Themes are defined in a properties file with the same name as the theme. For example, the default theme is defined as a set of entries in default.properties. For example, default.properties might define:

css ../screen.css
template template.xhtml

Usually the entries in a theme resource bundle will be paths to CSS styles or images and names of facelets templates (unlike localization resource bundles which are usually text).

Now we can use these entries in our JSP or facelets pages. For example, to theme the stylesheet in a facelets page:

<link href="#{theme.css}" rel="stylesheet" type="text/css" />

Most powerfully, facelets lets us theme the template used by a <ui:composition>:

<ui:composition xmlns="http://www.w3.org/1999/xhtml"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:f="http://java.sun.com/jsf/core"
    template="#{theme.template}">

Just like the locale selector, there is a built-in theme selector to allow the user to freely switch themes:

<h:selectOneMenu value="#{themeSelector.theme}">
    <f:selectItems value="#{themeSelector.themes}"/>
</h:selectOneMenu>
<h:commandButton action="#{themeSelector.select}" value="Select Theme"/>

The locale selector, theme selector and timezone selector all support persistence of locale and theme preference to a cookie. Simply set the cookieEnabled configuration property:

<component name="themeSelector">
    <property name="availableThemes">
        <value>default</value>
        <value>accessible</value>
        <value>printable</value>
    </property>
    <property name="cookieEnabled">true</property>
</component>

<component name="localeSelector">
    <property name="cookieEnabled">true</property>
</component>